Fluid operated device



Jan. 13, 1970 J, D, 5N|TGEN 3,488,957

FLUID OPERATED DEVICE Filed May 29. 1958 5 Sheets-Sheet l I N VENTOR.

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FLUID OPERATED DEVICE 5 Sheets-Sheet 2 Jan. 13, 1970 Filed May 29. 1968 Jan 13, 1970 -.'J. D. sNlTG'x-:N

FLUID @PERATED DEVICE 5 Sheets-Sheet 3 Filed May 29, 1968 .w OMM HITTIIIIHT J| WKN J NN NNN RNJNNNU NNN NNN NNN A NNN .NNNN NNN \NN\ NNN N NNN NNN NNN NNN NNN N NNN 5w E NNN RNNN NN MN United States Patent O M 3,488,957 FLUID OPERATED DEVICE Joseph D. Snitgen, 9656 Artesian, Detroit, Mich. 48228 Filed May 29, 196s, ser. No. 733,106 Int. Cl. F15b 15/14 U.S. Cl. 60-54.5 12 Claims ABSTRACT OF THE DISCLOSURE Several embodiments of fluid operated devices for applying a force to a workpiece, each of which is fluid pressure responsive and lwhich embodies a fluid force intensifying system. Each embodiment includes a fluid motor having a piston exposed on its opposite sides to respective first and second uid chambers and a -force applying device that is adapted to contact a workpiece and which is connected by means of a lost motion connection to the piston. The force applying device also has a portion-that is adapted to be exposed to the fluid pressure in one of the fluid chambers. The effective areas of the piston in the respective fluid chambers is such that the piston is in a state of fluid equilibrum when each of the chambers is exposed to substantially the same fluid pressure. One of the chambers is exposed to a substantially greater pressure than the other chamber to move the piston to a retracted position and to move the force applying member to its retracted position through the lost motion connection. When both of the fluid chambers are exposed to the same pressure, the fluid pressure acting on the force applying device moves the force applying device from its retracted position toward a force applying position. The lost motion connection also transmits this movement of the force applying device into simultaneous movement of the piston. Subsequent increase of the pressure in the other fluid chamber with respect to the first fluid chamber causes the piston to move to its force applying position. This movement of the piston accomplishes a hydraulic force intensification upon the force applying device so that an amplified force will be exerted upon the engaged workpiece. In two of the embodiments, the hydraulic force intensification is achieved by a hydraulic force intensifier that includes a substantially incompressible liquid that fills at least the chamber that is in fluid communication with the force applying device. In the other embodiment, the hydraulic force intensifying device has its own closed liquid system and the piston forms a reservoir for this system.

BACKGROUND OF THE INVENTION This invention relates to a fluid operated device and more particularly to several embodiments of fluid operated devices for applying an intensified force against a workpiece.

This application represents, in some regards, several improvements over my copending patent application of the same title, Ser. No. 621,511, filed Mar. 8, 1967, now Patent No. 3,410,089. In that application, a force intensifying device is disclosed in which a first fluid motor operates a fluid pump which, in turn, transmits an amplified force signal to a second fluid motor. The force amplification becomes operative when a contact or force applying member, which is the output member of the second fluid motor, reaches a predetermined position. The device shown in that patent application embodies a spring biased lost motion connection for permitting relative movement between the components of the fluid pump when the predetermined location is reached. It is upon this relative motion that the force amplification results. Although the device shown in that application is highly useful in many 3,488,957 Patented Jan. 13, 1970 ICC embodiments, such as in spot Welding apparatus, punch presses or the like, the use of the spring reduces, to some extent, the amount of force amplification permissible within a given overall dimension. In addition, the use of the spring may cause variations in the output force of the unit since a very small change in the preload upon the spring has a relatively large effect on the force output. It is also more difllcult to change the stroke of the amplifying device shown in that application.

It is, therefore, a principal object of this invention to provide an improved force applying device of the aforenoted character.

It is another object of this invention to provide a fluid operated force applying device that does not require springs or like members.

It is a further object of this invention to provide a hydraulic force applying device that achieves a relatively large force intensification from a given input signal.

It is yet another object of this invention to provide a hydraulic force applying device that is operable over a large stroke range.

It is still another object of this invention to provide a hydraulic force intensifier having a high efllciency.

The force applying device shown in the aforenoted patent application also embodies two different operating fluids. That is, the force amplifying unit employs a substantially incompressible liquid whereas the main motivating force is provided by a pneumatic cylinder or the like. This construction requires the provision of a separate fluid reservoir to accommodate the liquid of the force amplifymg unit.

It is, therefore, another object of one embodiment of this invention to provide a force amplifying device that does not require a separate reservoir and which may use only a single operating fluid.

It is also an object of another embodiment of this invention to provide a force applying device embodying the improved fluid reservoir for a force amplifying unit.

SUMMARY OF THE INVENTION A fluid operated force applying device embodying this invention is particularly adapted for exerting an amplified force against a workpiece from a given input signal. The device is comprised of a fluid motor and interrelated force applying member. The fluid motor has first and second relatively movable members that define spaced first and second fluid chambers. The second member is movable relative to the first member between a retracted position and a force applying position; and the force applying member is also supported for movement relative to the first member between a respective retracted position and a force applying position. The force applying member has a portion exposed to the fluid pressure in one of the fluid chambers and is interconnected to the second member by means of a lost motion connection which limits the relative movement between the second member and the force applying member in at least one direction. Fluid pressure means are provided for selectively varying the pressure within the first and second fluid chambers to operate the device. The fluid pressure means exposes the second fluid chamber to a substantially greater pressure than the rst fluid chamber for moving the second member to its rctracted position and for moving the force applying member to its retracted position through the lost motion connection. The fluid pressure means is also adapted to selectively expose both of the fluid chambers to substantially the Asame fluid pressure and for exerting substantially the same fluid force on opposite sides of the second member whereby the second member is in a state of fluid equilibrium. In this condition, the fluid pressure acting on the portion of the force applying member through the one lluid chamberis elective to move the force applying member from its retracted position toward its force applying position and for moving the second member from its retracted position toward its force applying position through the lost motion connection. In order to achieve an increased force upon the workpiece, the iluid pressure means is adapted to selectively expose the first fluid chamber to a substantially greater pressure than the secondfluid chamber for completing the movement of the second member to its force applying position. This movement is transmitted to movement of the force applying member through force transmitting means.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a cross-sectional view of a fluid operated force applying device incorporating a first embodiment of the invention and shows the devce in a retracted position.

FIGURE 2 is a cross-sectional View of the device shown in FIGURE l and illustrates the device in its extended, operative position.

FIGURE 3 is a cross-sectional view, in part similar to FIGURE l, Showing a second embodiment of the invention in a retracted position.

FIURE 4 is a cross-sectional view of the device shown in FIGURE 3 and illustrating the device in an extended, operative position.

FIGURE 5 is across-sectional view, in part similar to FIGURES 1 and 3, showing a third embodment of the invention in its retracted position.

FIGURE 6 is a cross-sectional view of the device shown in FIGURE 5 and illustrating the device in its extended, operative position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the invention is identified generally by the reference numeral 11 in FIGURES 1 and 2. In this embodiment, a fabricated housing assembly 12 is provided which consists of a tubular member 13 that denes a cylinder bore 14 closed at its opposite ends by end closure members 15 and 16.

An annular piston, indicated generally by the reference numeral 17, is positioned within the housing 12 and includes a piston portion 18 having an outer diameter that is slidably engaged wth the cylinder bore 14. An annular O-ring seal 19 is received in a circumferential groove 21 formed in the piston portion 18 to effect a fluid tight seal between the piston 17 and housing 12 and to divide the cylinder bore 14 into two, spaced variable volume lluid chambers 22 and 23. A port 24 extends through the closure member 15 from the chamber 22 and terminates in a tting receiving opening 25 so as to control the uid pressure in the chamber 22 in a manner which will become more apparent as this description proceeds. In a like manner, a port 26 extends through the closure member 16 from the chamber 23 and terminates in a fitting receiving opening 27 so that the pressure within the chamber 23 may be controlled in a manner which will also become more apparent as this description proceeds. An O-ring seal 28 positioned in a circumferental groove 29 in the closure member 15 appropriately seals the Huid chamber 22 from the atmosphere. An O-ring seal 31 positioned in a circumferential groove 32 formed in the closure member 16 seals the chamber 23 from the atmosphere.

The piston 17 is formed -with a concentric cylindrical bore 35 that extends through one of its ends from a reduced diameter cylindrical portion 36 formed on the side of the piston portion 18 in the lluid chamber 22. The bore 35 continues past the piston portion 18 into a cylindrical portion 37 which has substantially the same diameter as the portion 36. The bore 35 terminates at a slightly larger diameter cylindrical bore 38 which extends through the remainder of the cylindrical portion 37 and terminates within the chamber 23.

The cylindrical bores 35 and 38 define a third fluid chamber 39. The chamber 39 is closed at one end by a cylindrical pilot portion 41 of the closure member 15 that extends into the bore 35 and which carries an O-ring seal 42 in a circumferential groove 43 at its inner end. The opposite end of the third uid chamber 39 is closed by a cylindrical extension 44 of a contact or force applying member, indicated generally by the reference numeral 45. The extension 44 is received in the cylinder bore 38 and carries an O-ring seal 46 in a circumferential groove 47 formed at its inner end.

The contact or force applying member 45 further has a second cylindrical portion 48 that is slidably supported in a cylindrical bore 49 in the closure member 16. An O-ring seal 51 carried in a circumferential groove 52 adjacent the bore 49 sealingly engages the contact member portion 48 to preclude fluid leakage in this area. The contact member 45 carries a contact portion 53 at its outer end that is adapted to engage a workpiece or the like.

A lost motion connection is provided between the piston 17 and contact member 45 for limiting the relative movement between these components. This lost motion connection is comprised of a pin 54 that is fixed in aligned, diametrically opposed holes 55 and 56 formed in the piston portion 37 to fix the pin 54 with respect to the piston 17. The pin 54 extends through an elongated slot 57 formed in the contact member portion 44 to provide the lost motion between the pin 54 and contact member 45. The degree of relative movement in either direction is limited by the contact of the pin 54 with the ends of the slot 57. In addition, the degree of outward movement of the contact member 45 with respect to the housing assembly 12 is limited by an annular stop surface 58 formed adjacent the outer end of the slot 57 integrally with the contact member 45. Inward movement of the contact member 45 relative to the housing 12 is limited by a pin 59 that extends through the stop member portion 48 adjacent the closure member 16. When the device is in its retracted position (FIGURE l), the pin 54 is at the extreme right hand end of the slot 57 and the contact member portion 44 is disposed at the extreme outward limit of its position relative to the piston 17.

One or more radially extending ports 61 psss through the piston portion 37 from the iluid chamber 23 to the uid chamber 39. When the ports 61 are opened, the chamber 39 will be exposed to substantially the same fluid pressure as that existing in the chamber 23. The piston 17 is held in its retracted position under this circumstance by suitably venting the chamber 22 to the atmosphere and by exposing the chamber 23 to an elevated pressure. The chamber 23 and chamber 39 are preferably illed with a substantially incompressible liquid and the same liquid may be contained in the chamber 22. Alternatively, the chamber 22 may be filled with some other fluid such as air. When the chamber 23 is under a higher pressure than the chamber 22, the piston 17 will be forced to the extreme right hand limit of its movement, as determined by the abutment of the end of the portion 36 with the end closure member 15. Although the chamber 39 is pressurized through the ports `61 tending to move the contact member 45 to the left, the area of the bore 38 is less than the effective area of the piston 17 with the chamber 23 so that the pressure acting upon the Contact member 45 to the left will not prohibit the return movement of the piston 17. The pressure acting on the contact member 45 will, however, retard movement of the piston 17 to its retracted position in this embodiment.

When it is desired to move the contact member part 53 toward engagement with a workpiece (not shown) the chambers 22 and 23 are exposed to the same pressure in any suitable manner. When the pressures in the chambers 22 and 23 are equal and the parts are in the position shown in FIGURE l, the pressures on the opposite sides of the piston 17 will also be equal and the pistons 17 will be in a state a iluid equilibrium. The pressure in the chamber 39 is substantially the same as the pressure in the uid chamber 23 so as to equalize the forces on the piston 17. However, the fluid pressure in the chamber 39 acts upon the right hand end of the contact member portion 44 and thus exerts a force on this member tending to drive it to the left. Since the pin 54 is at the end of the slot 57, the lost motion connection will cause the piston 17 to be moved along with the contact member 45. This movement may continue for any portion of the stroke of the piston 17 and contact member 45 and preferably continues until the contact member part 53 engages the workpiece. At that time, the contact member part 53 will exert a force on the workpiece equal to the pressure in the chamber 39, which is equal to the pressure in the chambers 22 and 23, multiplied by the area of the end of the contact member portion 44.

At this time, the force exerted by the contact member 45 on the workpiece may be amplified by venting the chamber 23 to the atmosphere while maintaining an el evated pressure in the chamber 22. Alternatively, a pressure differential between the chambers 22 and 23 may be achieved in any other known manner. When a pressure differential exists between these chambers, a force will be exerted upon the piston 17 tending to move it to the left. Since the contact member 45 is now engaged with the workpiece, its movement will be restrained and the piston 17 will move relative to the contact member 45 and the ports 61 will become masked or closed o by the portion 44 of the contact member 45 (FIGURE 2). A hydraulic lock will then be established with the chamber 39. The chamber 39 and components which define it act as a force amplifier. That is, a shoulder 65 formed between the bores 35 and 38 acts as a piston, which pistou tends to compress the fluid in the chamber 39 and transmits a force against the piston defined by the end of the contact member portion 44. Since this latter area is substantially greater than the area of the shoulder 65, a hydraulic force amplification will result. Thus, the hydraulic or fluid force in the chamber 22 acting on the piston 17 is amplified within the chamber 39 so that the contact member portion 53 exerts an increased force against the workpiece.

In order to move the device 11 to its retracted position, the chamber 22 is vented to the atmosphere and the chamber 23 is subjected to a source of high pressure in any known manner. Alternatively, Athe chamber 23 is raised to a higher pressure than that existing in the chamber 22 in any other way. When the pressure in the chamber 23 exceeds the pressure in the chamber 22, the piston 17 will commence to move to the right as viewed in FIGURE 2 from its extended force applying position back toward its retracted position. During the initial phase of this movement, the pin 54 will retraverse the slot 57 and the contact member 45 will undergo little if any movement. Once the pin 54 reaches the end of the slot 57, the contact member 45 will also be retracted to the position shown in FIGURE 1 and the ports 61 will be reopened. Although the pressure in the chamber 39 under this condition acts against the retarding movement of the piston 17, the area of the contact member exposed to the pressure in the chamber 39 is less than the area of the piston 17 exposed to the pressure in the chamber 23.

The embodiment shown in FIGURES 3 and 4 is substantially the same as the embodiment shown in FIG- URES l and 2. For this reason, like components of this embodiment have been identified by the same reference numerals as those used in connection with the description of the embodiment of FIGURES l and 2 with the prefix l added. Components in the embodiment of FIG- URES 3 and 4 that are identical to those of the ernbodiment of FIGURES l and 2 will not 'be described again in detail. In this embodiment, the cylindrical portion 136 of the piston 117 is substantially longer than the cylindrical portion 137. The bore 135 terminates within the portion 137 and the bore 138 extends through the cylindrical portion 137 past the piston part 118 and into the cylindrical portion 136. Thus, the third fluid Cil chamber 139 of this embodiment is disposed on the side of the piston part 118 adjacent the first fluid chamber 122 rather than adjacent the chamber 23 and on the other side of the piston part 18 as in the previously described embodiment. In this embodiment, the chamber 137 is in fluid communication with the chamber 122 Avia. radially extending ports 161.

In all other respects than those mentioned above, the embodiment shown in FIGURES 3 and 4 is identical to the embodiment of FIGURES l and 2. It was noted in connection with the description of the operation of the previously described embodiment, that the fluid com munication between the chamber 39 and the chamber 23 tended to generate a force on the piston 17 through the lost motion connection which retarded the retraction of the piston 17. In this embodiment of FIGURES 3 and 4, the chamber 139 communicates with the charnber 122 rather than with the chamber 123 and the unit 111 `will retract at a faster rate than the previously described unit. The operation is otherwise the same in this embodiment.

In each of the previously described embodiments, the contact or force applying member had a portion that comprised an output piston of a hydraulic force intensifying device. The force intensification was accomplished through the use of a substantially incompressible fluid which filled at least; the chamber of the main fluid motor that was in communication with the force intensifying device. As was noted in each of the previously described embodiments, the same fluid could be contained in the entire unit. The construction of those embodiments was such that a separate reservoir was not required to contain the incompressible fluid in counterdistinction to the unit shown in my aforenoted copending application. The embodiment of FIGURES 5 and 6 has substantially the same sequence of operation as the embodiments of FIG- URES l through 4; however, this embodiment is intended to use two different fluid mediums and the incompressible liquid of the force intensifying device requires a separate reservoir. The reservoir shown in this embodiment, however, is more compact and easier to form than the reservoirs shown in my aforenoted copending application. In addition, the embodiment of FIGURES 5 and 6 has certain of the other aforenoted advantages over the device shown in my aforenoted patent application.

Referring now specifically to FIGURES S and 6, a third embodiment of a fluid operated force applying device is identified generally by the reference numeral 201. The device 201 is comprised of an outer housing assembly 202 that consists of a tubular member 203 that defines an internal lbore 204 which is closed at its opposite ends by end closure members 205 and 206, which closure members are affixed to the tubular member 203 in any suitable manner.

A piston, indicated generally by the reference numeral 207, is slidably supported within the bore 204 and divides the bore 204 into first and second spaced fluid chambers 208 and 209. A port 211 extends through the tubular member 203 into an annular clearance which exists between the outer periphery of the piston 207 and the bore 204 when the piston 207 is in its retracted position (FIGURE 5). A fluid such as high pressure air may be introduced into the chamber 208 through the port 211 by means of a suitable fitting 212 and control valve (not shown). Alternatively, the chamber 208 may be pressurized through a passage 213 formed in a cylindrical extension 214 of the closure member 205. The extension 214 is formed with a tapped opening 215 to receive an appropriate fitting or closure member depending upon which of the ports 211 or 213 is utilized to control the pressure within the chamber 208.

A port 216 is formed in the tubular member 203 adjacent the inner end of the closure member 206 and within the chamber 209. A fitting 217 is aflixed to the housing 202 adjacent the port 216. The pressure within the chamber 209 may be appropriately controlled through the port 216 and fitting 217 by connecting the tting 217 via a valve to any suitable Huid pressure source, for example to a source of high pressure air. Leakage between the chambers 208 and 209 is precluded by means of an O-ring seal 218 that is contained within a circumferential groove 219 formed around the periphery of the piston 207 on the end of the piston adjacent the chamber 209.

A force applying or contact member, indicated generally by the reference numeral 221, has a cylindrical portion 222 that is adapted to Contact and apply a force against a workpiece. A larger diameter, cylindrical portion 223 is slidably supported in a bore 224 formed concentrically in the end closure member 206. The bore 224 extends through one end of the closure member 206 and terminates at its other end adjacent a reduced diameter bore 225 to provide a shoulder 226. A cylindrical extension 227 of the contact member 221 is slidably supported within the bore 225. An O-ring seal 228 received in a cylindrical groove 229 of the closure member 206 at one end of the bore 224 precludes fluid leakage in this area. An O-ring seal 231 is positioned in a cylindrical groove 232 formed adjacent the bore 225 sealingly engages the contact member portion 227 to insure against fluid leakage in this area.

A rst cylindrical bore 235 is formed in the outer end of the contact member 221 and extends from a tapped opening 236 through the portion 222 into the portion 223. The outer end of the bore 235 is closed by means of a closure plug 237 which carries an O-ring seal 238 and which is threaded into the tapped opening 236. The bore 235 terminates adjacent a smaller diameter bore 239 that extends through the remainder of the portion 223 and partially into the portion 227 of the contact member 221. The inner end of the bore 239 terminates adjacent a larger diameter bore 241 which, in turn, extends through the outer end of the portion 227. The bore 241 is closed by means of a closure plug 242 that is received on a threaded end 243 of the contact member portion 227.

A piston member 244 has a threaded end 245 that is received in a tapped opening 246 formed in a head 247 of the piston 207 adjacent the chamber 209. The piston member 244 extends through an opening 248 in the closure plug 244 and is sealingly engaged by means of an O-ring seal 249. The piston member 244 has an enlarged cylindrical projection 251 that is complementary in shape to the bore 241 and which is received therein. On the outer side of the portion 251, the piston member 244 has a portion 252 that extends into the bore 239 and which carries an O-ring seal 253 that sealingly engages this bore.

A diagonally disposed uid passage 254 extends from the outer end of the bore 239` to a Huid chamber 255 that is formed between the shoulder 226 and an oppositely facing shoulder 256 formed by the contact member 221 at the juncture of the portions 223 and 227.

One or more passages 257 also extend from the bore 239 through the member 221 into a chamber 258 formed between the bore 241 and the piston member portion 252. The passages 257 terminate at the bore 239 in ports or openings 259 that are disposed contiguous to the end of the bore 239 opposite to that intersected by the passage 254.

The chamber 258 is also intersected by a plurality of radially extending passages 261 formed in the piston member portion 252, which passages also intersect an axially extending passage 262. The passage 262 extends through a part of the piston member portion 252 and through the threaded end 244 into a iluid reservoir 263 formed in part by a cylindrical bore 264 of the piston 207. One end of the bore 264 and reservoir 263 is closed by the piston head 247 with the other end being closed by a floating piston 265. The piston 265 carries an O-ring seal 266 in a circumferential groove 267 to sealingly engage the piston 207. The extreme outer movement of the floating piston 265 with respect to the piston 207 is limited by a snap ring 268 contained within a circumferential groove 269 formed in the piston 207. l

In operation, the device 201 like the devices of the previously described embodiments may be used for a wide variety of purposes. One of such purposes is in connection with spot welding and to this end the force applying member 221 is held against rotation by means of a pin 271 that is press tted into the contact member portion 223 and which extends into an axially extending slot 272 formed in the closure member 206.

FIGURE 1 illustrates the device 201 in a fully retracted position wherein both the piston 207 and contact member 221 are retracted to the extreme innermost limitation of their strokes. When it is desired to move the contact member 221 toward the workpiece, both the chambers 208 and 209 are exposed to substantially equal uid pressure by any suitable means. As in the previously de- -scribed embodiments, the piston 207 has substantially equal effective areas disposed to the pressures in these chambers and, therefore, the piston 207 itself is in a state of fluid quilibrium. The portion of the contact member 221 disposed in the chamber 209, however, provides an eiec* tive piston area in this chamber upon which the iluid pressure acts. This pressure acting on the member 221 causes it to be driven to the left as viewed in FIGURE 5. Movement of the contact member 221 to the left is transmitted from the end closure cap 242 to the piston member por tion 251 and, accordingly, to the piston 207 so that the piston 207 also moves to the left. During the movement of the contact member 221 and piston 207 to the left the Volume of the chamber 255 will increase. This chamber as well as the bores 235, 239, chamber 258, passages 254, 257, 262, 261 and reservoir 263 are filled with a substantially incompressible liquid. This liquid flow-s from the reservoir 263 through the passages 262, 261, chamber 258, passages 257, bore 239 and passage 254 to the chamber 255. As the liquid is thus transferred from reservoir 263, the oating piston 265 moves axially inwardly along the bore 264 under the force of the fluid pressure in the chamber 208.

The simultaneous movment of the piston 207 and contact member 221 may be continued in the aforenoted manner until the outer end of the contact member 221 engages the workpiece. At that time, the contact member 221 will exert a relatively low force upon the workpiece. In order to achieve a force amplification at this time, the pressure in the chamber 208 is increased significantly over the pressure in the chamber 209, for example by venting the chamber 209 to sump. A pressure differential will now exist on the piston 207 and the piston 207 will move to the left whereas the contact member 221 will be held against any substantial movement by its engagement with the workpiece. Since a lost motion connection exists between the piston 207 and contact member 221, this relative movement is permitted. After a predetermined degree of relative movement, the end of the piston member portion 252 will move into registry with the ports 259 and will eventually close off these ports (FIGURE `6). When this occurs, the incompressible liquid is trapped in the bores upon the workpiece through the contact member 221.

In order to retract the piston 207 and contact member 221, the pressure in the chamber 209 is raised substantially above the pressure in the chamber 208. This may be done in any suitable manner, as by venting the chamber 208 to sump and exposing the chamber 209 to a source of elevated pressure. The pressure acting on the head 247 of the piston 207 causes the piston 207 to move toward the right from its position shown in FIGURE 6. Initially the contact member 221 will not undergo any movement since the pressure in the chamber 209 tends to hold the contact member 221 in its extended position. The relative return movement between the piston 227 and contact member 221 continues until the piston member portion 251 retraverses the bore 241 and engages the end closure cap 242. At this time, the piston 207 and contact member 221 will move in unison toward the right and toward their retracted position as shown in FIGURE 5. Since the piston 207 has a greater effective area disposed to the pressure in the chamber 209 than the area of the contact member 221, retraction will continue when the lost motion has been taken up between these two elements. When the contact member 221 moves to the right, the fluid in the chamber 255 will be displaced through the passage 254 and may refill the reservoir 263 since the ports 259 will now be open.

It should be readily apparent that in each of the disclosed embodiments a force amplification is provided that is substantially independent of position. That is, the devices are not position responsive and, therefore, may operate over a wide range of strokes. Other various advantages of the embodiments have been previously described and will not be repeated here.

While it will be apparent that the preferred embodiments of the invention disclosed herein are Well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A fluid operated force applying device comprised of a fluid motor having first and second relatively movable members defining spaced first and sec-ond fluid chamber; said second member being movable relative to said first member between a retracted position and a force applying position; a force applying member adapted to engage a workpiece or the like; means for supporting said force applying member for movement relative to said first member between a retracted position and a force applying position; said force applying member having a portion exposed to the fluid pressure in said second fluid charnbe'r; lost motion connection means operatively connecting said second member with said force applying member for limiting relative movement between said second member and said force applying member in at least one direction; means for selectively exposing said second fluid chamber to a substantially greater pressure than said first fluid chamber for moving said second member to its retracted position and for moving said force applying member to its retracted position through said lost motion connection means, for selecively exposing both of said fluid chambers to substantially the same fluid pressure for exerting substantially the same fluid force on opposite sides -of said second member whereby said second member is in a state of fluid equilibrium, the fluid pressure acting on said portion of said force applying member through said second fluid chamber when both of said chambers are exposed to substantially the same pressure being effective to move said force applying member from its retracted position toward its force applying position and for moving said second member from its retracted position toward its force applying position through said lost motion connection means, and for selectively exposing said first fluid chamber to a substantially greater pressure than said second fluid chamber for completing the movement of said second member to its force applying position; and force transmitting means for moving said force applying member to its force applying position in response to movement of said second member to its force appling position.

2. A fluid operated force applying device as set forth in claim 1 wherein the force transmitting means includes means for amplifying the force signal transmitted by the second member to the force applying member.

3. A fluid operated force applying device `as set forth in claim 1 wherein the first member comprises means defining a cylinder bore, the second member comprising a piston slidably supported in said cylinder bore.

4. A fluid operated force applying device as set forth in claim 3 wherein the force transmitting means includes means for amplifying a force signal transmitted from the piston to the force applying member.

S. A fluid operated force applying device as set forth .in claim 4 wherein the force amplifying means comprises piston means fixed relative to the second member and acting upon a substantially incompressible liquid and second piston means fixed relative to the force applying member and against which said incompressible liquid acts, said first mentioned piston means having a substantially smaller area than said second piston means.

6. A fluid operated force applying device as set forth in claim 5 wherein the first mentioned piston means is an annular piston formed concentrically in the second member and the second piston means comprises a portion of said force applying member slidably supported within a bore in said second member.

7. A fluid operated force applying device as set forth in claim 6 further including port means extending through the second member from the second fluid chamber, said portion of said force applying member being adapted to close said port means upon relative movement between said second member and said force applying member for locking fluid within the cylindrical bore of the second mem-ber.

8. A fluid operated force applying device as set forth in claim 6 further including port means extending through the second member from the first fluid chamber, said portion of said force applying member being adapted to close said port means upon relative movement between said second member and said force applyin-g member for locking fluid within the cylindrical bore of the second member.

9. A fluid operated force applying device comprising housing means defining a cylinder bore, an annular piston slidably supported in said cylinder bore and dividing said cylinder bore into first and second spaced fluid chambers, a third fluid chamber formed in part by said annular piston, said third fluid chamber being defined by first and second portions formed in said annular piston and extending through said annular piston to said first and second fluid chambers, respectively, said second portion of said third fluid chamber having a greater crosssectional area than said first portion, said housing means forming a pilot member at one end thereof extending into said rst portion of said third fluid chamber for forming a closure for one end thereof, a force applying member extending in part from the other end of said housing means and adapted to contact a workpiece for exerting a force thereagainst, said force applying member having a part extending into said second portion of said third fluid chamber for forming a closure for the other end thereof, means providing a lost motion connection between said annular piston and said force applying member for limiting the relative movement therebetween, fluid passage means for communicating the fluid pressure from on'e of said first and second fluid chambers to said third fluid chamber, said part of said force applying member being adapted to close said fluid passage means upon a predetermined degree of movement of said annular piston relative to said force applying member for establishing a fluid lock within said third fluid chamber, and means for selectively exposing said first and said second fluid chambers to substantially the same fluid pressure for exerting the same fluid force on opposite sides of said annular piston whereby said annular piston is in a state of fluid equilibrium, the fluid pressure exerted in said third fluid chamber through said fiuid passage means acting on said force applying member for moving said force applying member from a retracted position toward a force applying position and for moving said annular piston through said lost motion connection from a retracted position toward a force applying position, said last named means being selectively operable to increase the iiuid pressure in said first fiuid chamber above the pressure in said second fiuid chamber for effecting a force on said annular piston to move said annular piston toward its force applying position and for closing said fiuid passage means whereby a hydraulic lock is effected in said third fluid chamber for effecting a force amplification upon said force applying member for moving said force applying member to its force applying position.

10. A fluid operated force applying device as set forth in claim 9 wherein the fluid passage means communicates fluid pressure from the first fluid chamber to the third fluid chamber.

11. A fiuid operated force applying device as set forth in claim 9 wherein the fiuid passage means communicates fluid pressure from the second fluid chamber to the third fiuid chamber.

12. A fiuid operated device for applying force to a workpiece or the like comprising housing means defining a first cylinder bore, a first piston supported for reciprocation Within said first cylinder bore and dividing said first cylinder bore into first and second spaced fiuid chambers, means for selectively pressurizing said first and second fluid chambers for reciprocating `said first piston within `said first cylinder bore, a force applying member supported for reciprocation within said housing means and having a projecting end adapted to engage a Workpiece, means defining a second cylinder bore in said force applying member, a second piston supported for reciprocation within said second cylinder bore, means for afiixing said Isecond piston to said first piston for simultaneous reciprocation of said first and said second pistons, lost motion connecting means interposed between said second piston and said force applying member for limiting the relative movement between 'said second piston and said force applying member, means in said housing means defining a third cylinder bore, means fixed to said force applying member defining a third piston supported for reciprocation Within said third cylinder bore, the effective area of said third piston being substantially greater than the effective area of said second piston, a variable volume liquid reservoir defined within said first piston, first fluid passage means extending through said force applying member from said second cylinder bore to said third cylinder bore on one side of said third piston, second fluid passage means extending from said liquid reservoir to said second cylinder bore, a liquid substantially filling said second cylinder bore, said third cylinder bore, said first and said second fiuid passage means and said reservoir, said lost motion connecting means providing for relative movement of said second piston and said force applying member for displacing liquid from said second cylinder bore into said third cylinder bore on said one side of said third piston through said first fluid passage means and means responsive to said relative movement between said second piston and said force applying member for precluding fluid fiow between said second cylinder bore to said reservoir through said second fluid passage means for generating a force amplification upon said force applying member by the liquid displaced from said second cylinder bore after said predetermined relative movement.

References Cited UNITED STATES PATENTS 3,276,206 10/1966 Calkins. 3,410,089 1l/1968 Snitgen.

MARTIN P. SCHWADRON, Primary Examiner R. R. BUNEVICH, Assistant Examiner U.S. Cl. X.R. -52 

